Sheet metal press



OI KUHNER SHEET METAL PRESS Filed Sept.

Jan. 10; 1933.

Patented Jan. 10, 1933 UNTED STATES OTTO K'HNER, OF GOPPINGEN, GERMANYSHEET METAL PRESS Applicatiomfiled September 3, 1930, Serial No.

My invention relates to sheet-metal presses, and more particularly tothe blank holders of such presses. In my copending ap lication forpatent of the United States, erial No. %48,676, filed April 30, 1930, Ihave described a press in which the blank holder is tted to slide in acavity of the drawing slide against the action of an air cushion, asshown in Fig. 2 of my' said copending application. lt is an object of myinvention to so design a device of this type that it is suitable forpresses having a comparatvely wide drawing slide, `tor instance, pressesfor drawing mud guards for motorcars, window frames and the like. Tothis end, instead of arranging the blank holder in, I a'rrange it on thedrawing slide, and provide means for entrappng a fluid cushion betweenthe drawing slide and the blank holder.

In this manner not only the press may be designed for any width but Ialso dispense with the packing for guiding the blank holder in thedrawing slide and furthermore I may provide some play between the blankholder and the drawing slide so that the blank holder is free to adaptitself to variations in the thickness of the blank material' and exertuniform pressure on the blank throughout.

' In the drawing a sheetmetal press embodying m invention is illustrateddiagram'- matically y way of example, the drawing showing a'partly'sectional elevation of the press. V

Referring now to the drawing, a s the main driving or crank shaft of thepress, b are its pitmen, d is the drawing slide, and c are ball jointsconnecting the pitmen b with the drawing slide d. e is the drawingblock, m is a blank, and f is the blank holder which engages the edge ofthe blank m and holds it down on the drawing block e. o, o are bracketsextending from the sides of the blank holder f, and n, n are slide barson which the brackets are guided. i Similar brackets p, p are providedon the sides of the drawing slide d extending through slots in the sidesof the blank holder f and also guided on the bars n.

is a fiange projecting inwardly from the 7 blank holder f, and g arep'neumatic cylin- &79,433, and"in Germany September& 19539.

ders Secured on the fiange. Two cylinders are shown by way of examplebut obviously any number of cylinders may be provided. Each cylinder isequipped With a piston h and a pisten rod z' which extends through abore and a packing Z in the fiange f', and m' is a spherica l joint atthe lower end of each piston rod by which it is connected to the drawingslide d. Ic are passages .connecting the space below the piston I) ineach cylinder g with a compressed-air reservoir, not shown.

In the position illustrated the drawing slide (Z is at the lowermost endof its stroke, and

the blank holder f is held on the edge of the blank by the pressure ofthe air below the pistons k. `When the'drawing slide d is reversed tomove upwards the blank holder f is still held down on the ed 'e of theblank by the air pressure, although the pressure is somewhat reduced bythe increase of Volume it has undergone. Finally the drawing' slide dengages below the flange f' and entrains the blank holder f. When thedrawing slide is reversed for another downward stroke the 'blank holderf moves down with the drawing slide until it strikes the edge of theblank m on the drawing' block e and is arrested, while the drawing slidemoves on, compressing the air below the pistons, dispelling it artlyinto the reservoir, no't shown, through t e passage k, and forging theblank m intothe shape indicated.

As shown, the drawing slide d is fitted into the blank holder f withsomeplay so that the blank holder is free to edge slightly if the ma- 35terial of the blank is not of quite uniform thickness. Its edging isfacilitated by the ball joints m'- at the lower ends of the piston rodsz' It will be understood that the blank holder is not guided on thedrawing slide but is guided on the bars n. Obviously, however, theguiding means must not interfere With its edging.

I wish itto be understood that I do not desire tobe limited to the exactdetails of construction shown and described for obvious modificationswill occur to a person skilled in the art.

In the claims afiixed to this specification'no selection of`-anyparticular modification of i the invention is intended to the exclusionof other modfications thereof and the right to v subsequently make claimto any modification not covered by these claims is expressly reserved.

I claim:

1. A sheet-metal press comprising a drawing slide, adapted to performits operation in a single stage, means for reciprocating 30 said drawingslide, a blank holder surrounding said drawing slide, a cylinder on saidblank holder, a piston in said cylincler, and a piston rod connectingsaid pisten to said drawing slide.

2. A sheet-metal press comprising a drawing slide, a blank holder soarranged on said drawing slide as 'w move freely within limits withrespect to said drawing slide, means for reciprocating said drawingslide, and pneumatic means operatively conneeting said blank holder tosaid drawing slide.

3. A sheet-metal press comprising a drawing slide, means forreciprocating said drawing slide, a blank holder surrounding saiddrawing slide at a clearance'so as to move freely within limits withrespect to said drawing slide, a cylinder on said blank holder, a pistonin said cylinder, a piston rod on said piston, and a universal jointconnecting said 0 piston rod to said drawing slide.

In testimony whereof I aflix' my signature.

"OTTO KlI-INER.

